Variable inductance



Feb. 12, 1929.

N. H. CLOUGH VARIABLE INDUCTANCE Filed June 27, 1925 INVENTOR NEWSOMEHENRY CLDUGH By '4 TTORNEY Patented Feb. 12, 1929.

UNITED STATES PATENT OFFICE.

NEWSOME HENRY CLOUGH, OF CHELMSFORD, ENGLAND, ASSIGNOR T RADIO COB-ZPORA'IION OF AMERICA, A CORPORATION OF DELAWARE.

VARIABLE INDUCTANGE.

Application filed June 27, 1925, Serial No. 39,895, and in Great BritainJuly 4, 1924.

This invention relates to variable inductances or variometers.

According to this invention 1 provide an inductance coil with a shieldwhich preferably takes the form of a split ring and with means forinterconnecting two variable points on the shield, so that a variablelength of the shield may be short-circuited. By this means a closedmetallic loop is provided and its area is variable from zero to the areaenclosed by the shield.

in one form of variometer l employ a cylindrical coil substantiallyenclosed in a shield formed of a metallic tube which is mountedcoaxially with the coil, and 1 conmeet one end of the tube to a spindlewhich can rotate about the axis of the coil and tube and carries an armor arms making rubbing contact with a surface or surfaces of the tube.29 Thus by rotating the spindle, a variable length of the tube can beshort-circuited and thus the inductance of the coil can be varied.

I may also employ a strip around the outside of the coil with meanssimilar to those for short-circuiting a. portion of the tube forshort-circuitiug a portion of the outer strip, or the strip may bearranged coaxially but not concentric with the coil.

Again, l may form the shield of a strip of foil which is wound upon abobbin and has one end fixed relative to the coil, the bobbin beingmounted on an arm which is rotatable about the axis of the coil, so thatby turning the arm more or less of the :toil can be unwound from thebobbin.

A more clear and complete understanding of my invention will be had fromthe following detailed description of the various modifications thereofwhen read in connection with the accompanying drawings throughout whichlike reference numerals indicate like parts and in which;

Figure l is a rear elevation view of one form of my invention showingthe split ring outside the coil.

Figure 2 is a sectional rear elevation of the same device shown inFigure 1.

Figure 3 is a modification or the arrangement shown in Figure 1 with ametal tube corresponding to the split ring in Figure 1,

Figure 4 is a part sectional rear elevation of the device shown inFigure 3,

Fl re 5 is a still further modification showing a metal foil to thesplit ring while,

Figure 6 is a rear elevation of the modification shown in Figure 5.

Referring in particular to the drawings one form of the invention isshown in Figs. 1 and 2 where the circular coil is indicated by numeral 1through the center of which extends the shaft 8 adapted to support asplit ring 2. The split ring 2 is supported out-- side the coil 1 fromshaft 8 and bushing or tube 7' by a fixed arm 17. Mounted upon the shaftor spindle 8is a movable arm 18 carrying the brushes 19 which areadapted to contact with the split ring 2 and upon rotation of the shaft8 by means of an actuating knob (not shown) to short-circuit a varyingamount of the ring 2' whereby the efiective coil length is changed so asto give the desired inductance.

Figures 3 and 4 show a further modification in which the coil 1 issurrounded by a split metal tube 20 supported in any preferred mannerfrom a shaft 8. Contact with one end of the tube, which may be, forexample, copper, is maintained'through an arm or fixed member 21 carriedby the shaft 8 and also carried by the shaft 8 is a rotatable arm orlever 22 adapted to carry brushes 28 which bear against and make contactwith opposite sides of the metal tube 20. In a manner similar to thearrangements shown in Figs. l and 2, the coil may be short-circuited soas to give any desired inductance by rotating the arm 22 in either aclockwise or countor-clockwise direction.

Still another embodiment which my invention may assume is shown in Figs.5 and 6 where the coil 1 is mounted on a support in the form of aninsulating disk 30 which also provides a bearing for a shaft 8 as shownin Figure 6 merely for purposes of illustration as this coil may bemounted in any convenient manner. (larried by the support 30 is a fixedarm 24 which is adapted to support a thin metal foil 28 which may befastened in any preferred means to this arm such as for example, byriveting. The arm 24 is mounted at one end of the coil and is bent toextend over the outer peripheryof the coil so that the metal foil 28 maysurround the coil in a manner similar to that of the split ring 2' showninFigs. i to 4. The shaft 8 which is rotatably mounted in the bearing ofsupport 30, carries at the other end of the coil an arm 25 which in turnsupports at the outer end thereof a pin 26 adapted to project across theouter periphery of the coil and to carry a bobbin 27. The metal foil 28is secured to this bobbin and is adapted to be wound on the bobbin whenshaft 8 is rotated in one direction and unwound therefrom when the shaft8 is rotated in the opposite direction. The bobbin may be provided withan internal spring, not shown, so as to keep the foil at all times tightand may be held in any desired position by the friction of the arm uponthe shaft. In this case, variances of inductance are ob tained byrotating the arm 25 so as to permit more or less of the metal foil 28 tosurround the coil 1 and vary the effective coil length.

7 Having now described my invention I claim:

1. In a variable inductance, the combination of a coil, means forvarying the inductance of said coil including a rotatable spindie withinsaid coil, a fixed arm mounted upon said spindle at one side of saidcoil and extending beyond the periphery of said coil, a rotatable arm.extending beyond said coil P81 riphery mounted upon said spindle at theother side of said 001 a rotatable bobbin carried by said rotatablearm,and a sheet of metal foil fastened to said fixed arm and adapted to windand unwind upon said bobbin.

2. In a variable inductance, the combination of a coil, means for varyinthe inductance of the coil including a flexibde metal foil sheet adaptedto be wrapped around the periphery of said coil, and means forwrappmg orunwrappin said metal sheet.

3. In a variable inductance, the combination of a coil, means forvarying the inductance of said coil comprising a support mounted in saidcoil, a metal shield surrounding a periphery of said coil, a fixedmember mounted on said support connected to one end of said shield, amovable member mounted on said support and a bobbin carried by saidmovable member and adapted to wind or unwind said shield when saidmovable member is moved.

nnwsonn HENRY OLOUGH.

